1. Field of the Invention
The present invention relates to a silane-modified biopolymeric, biooligomeric, oxidic or siliceous filler, a process for its production and its use.
2. Description of the Background
The treatment of oxidic or siliceous compounds with organosilicon compounds in order by means of this treatment to strengthen the bond between the inorganic filler and the organic polymer used in filler-reinforced elastomers, and hence to improve the properties of the fillers in the polymers, is known.
It is known from DE 2141159, DE 2212239 and U.S. Pat. No. 3,978,103 that sulfur-containing organosilicon compounds such as bis(3-triethoxysilylpropyl) tetrasulfane or 3-mercaptopropyltriethoxysilane are used as silane bonding agent or reinforcing filler in oxidically filled rubber compounds, for tire treads and other automotive tire components among other things.
The use of mercaptosilanes in rubber compounds for tire treads is known from FR-A 152.094.859.
In order to circumvent the considerable problems in the processing of mercaptosilanes, such as pre-scorch, scorch and plasticity properties for example, polysulfidic organosilanes such as e.g. bis(3-triethoxysilylpropyl) tetrasulfane or bis(3-triethoxysilylpropyl) disulfane (DE 2542534, DE 2405758, DE 19541404, DE 19734295) are mostly used as a coupling agent for tire components, representing a compromise for silica-filled vulcanisates in terms of vulcanisation safety, ease of production and reinforcing performance.
The corresponding additives, especially the organosilanes and the unmodified fillers, can be introduced into the unvulcanised polymer blends in various ways.
The in-situ method involves a combined mixing process for fillers, such as carbon black and silica, organosilanes and polymer.
The ex-situ method involves modifying the filler with the corresponding organosilane or combining a mixture of various organosilanes before mixing the filler with the polymer.
It is known that the filler surface can be modified by dissolving the organosilicon compound in an organic solvent with subsequent treatment of fillers, e.g. clays (U.S. Pat. No. 3,227,675).
Liquid addition (U.S. Pat. No. 3,997,356) or addition of the active filler by means of a pre-produced physical blend of organosilane and filler (DE 3314742, U.S. Pat. No. 4,076,550) is particularly important today. The disadvantages of these blends, which do not undergo any thermal pretreatment, lie in their storage stability and hence in the stability of the product properties.
U.S. Pat. No. 4,151,154 describes oxidic siliceous fillers, the surface of which undergoes treatment with two different types of organosilicon compounds. The oxidic particles are treated in such a way that they exhibit a greater affinity to water and can also be more easily dispersed in aqueous systems.
The modification of kaolin suspended in water with various silanes is known from U.S. Pat. No. 3,567,680. The organosilicon compounds that are described are water-soluble in the quantities required for the modification, however, which means that in this case the filler can be treated from an aqueous solution.
U.S. Pat. No. 4,044,037 describes aryl polysulfides and mineral fillers treated with these compounds, which are used in rubber compounds. They are produced in an aqueous/alcoholic formulation containing 99.9 to 80 wt. % alcohol.
Moreover, a process in which the surface of siliceous fillers is modified with the aid of an aqueous emulsion of water-insoluble organosilicon compounds is known from EP-PS 01 26 871.
The known fillers modified ex situ with silane have the disadvantage that the dynamic rubber properties tend to be worse rather than the same as or better than those of fillers and silanes mixed together in situ. In the case of fillers with a large specific surface area or a raised surface texture, impregnation is not homogenous but instead is mostly confined to a thin surface layer and is therefore unsatisfactory.
The known methods for modifying fillers for rubber and plastic applications with surface-active silanes or mixtures thereof are based on the use of water, organic solvents or the direct spraying of the organosilicon compound onto the surface of the filler with a subsequent conditioning reaction. The water-insoluble, rubber-typical silanes can only be converted into hydrocarbon-based solvents, which are generally toxic and highly flammable.
Accordingly, there remains a need for silane-modified fillers which overcome these disadvantages.